The solubilization of extruded (100 nm) unilamellar egg yolk phosphatidylcholine (EYPC) liposomes by a series of N-alkyl-N,N-dimethylamine N-oxides (CnNO, n=10–14 carbon atoms in the alkyl substituent) was studied using turbidimetry. The solubilizing concentration of CnNO (cS) was estimated as the CnNO concentration causing the half-maximum decrease in turbidance. From the linear cS dependence on EYPC concentration, the lipid – aqueous phase molar partition coefficient (Kp) and theCnNO:EYPCmolar ratio in theCnNO+EYPCaggregates (nL:nEYPC) at cS wereobtained: Kp=82±25 and nL:nEYPC =0,70±0,20 for C10NO, Kp=507±215 and nL:nEYPC =0,60±0,16 for C12NO, and Kp=12357±93 and nL:nEYPC =1,13±0,01 for C14NO. The value of Gibbs free energy of CnNO alkyl methylene group transfer from the aqueous to the lipid phase calculated from the Kp dependence on n is -1,2±0,2 RT (R=gas constant, T=absolute temperature), within the experimental error being the same as -1,026±0,006 RT obtained from the critical micellar concentrations ofCnNO. The increased value of nL:nEYPC for C14NO is caused by the decreased hydrophobic mismatch of CnNO and EYPC hydrocarbon chain lengths. This mismatch results in a structural defect in the bilayer hydrophobic core, the primary cause of bilayer destabilization and solubilization.

        Key words: solubilization – liposome – bilayer – N-alkyl-N,N-dimethylamine N-oxide – phosphatidylcholine